Đáp án:
Giải thích các bước giải:
x³ - 7x² - 9x + 63 = 0
(x³ - 7x²) -(9x - 63) = 0
x²(x - 7) - 9(x - 7) = 0
(x - 7).(x² - 9) = 0
(x - 7).(x - 3).(x + 3) = 0
⇔ x - 7 = 0 hoặc x - 3 = 0 hoặc x + 3= 0
⇔ x = 7 hoặc x = 3 hoặc x = -3
Vậy x = 7 , x = ± 3
$ x^{3} - 7x^{2} - 9x + 63 = 0 $
$⇒ x^{2} ( x - 7 ) - 9 ( x - 7 ) = 0 $
$ ⇒ ( x^{2} - 9 ) ( x - 7 ) = 0 $
$ ⇒ $\(\left[ \begin{array}{l}x^{2}-9=0\\x-7 =0\end{array} \right.\)
$ ⇒ $ \(\left[ \begin{array}{l}x=±3\\x=7\end{array} \right.\)
Vậy $ x ∈ { -3 ; 3 ; 7 } $
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Cho m gam hỗn hợp CaCO3 và KHCO3 tác dụng với lượng dư dung dịch HCl, sau phản ứng thu được 4,48 lít khí CO2 (ở 0độC, 2 at). Tính m.
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Rút gọn a. Căn bậc 2 của 84^2 - 37^2 / 47
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